This invention relates to an induction system for a multi-cylinder engine having multiple carburetor barrels and more particularly to such an induction system that offers improved combustion and efficiency throughout the entire engine range and provides for smooth transitional operation.
Recently it has been discovered that engine operation (both emission of unwanted exhaust gas constituents and fuel economy) can be improved, particularly at idle and low load operation by providing a sub-intake system through which a substantial portion of the induction charge flows to the combustion chambers under these operating conditions. By using a relatively small cross-sectional area induction system turbulence and, if desired, swirl may be generated in the combustion chamber at the time of ignition. As such, smoother and more efficient combustion results under these load conditions.
It has been proposed to control the flow through the sub-intake system by means of a main throttle valve and an auxiliary or sub-throttle valve which operate in sequence so as to cause substantially all of the idle and low load charge requirements to enter the combustion chambers through the sub-intake passage and to provide an increased flow through the main induction passage as the engine load increases. In connection with the adaptation of this concept to multiple chamber engines having multiple carburetor barrels, it has been proposed to provide only one of the carburetor barrels with a system for accomodating certain engine operating conditions. This one carburetor barrel can serve a plurality of chambers through the combined sub-intake passages, all of which are fed from this one carburetor barrel. An example of an application of this principal to a multiple cylinder engine may be found in the copending application of Hiromitsu Matsumoto, Ser. No. 838,353, entitled Control of Carburetor Supplied Induction System, filed Sept. 30, 1977 and assigned to the assignee of this application, such an arrangement being shown specifically in the embodiment of FIGS. 6-10 of that application. With such an arrangement where one carburetor barrel serves a plurality of chambers, it is advantageous if this one carburetor barrel provides the idle and low speed requirements of the engine through the auxiliary or sub-intake passages. During the transitional stage from the running characteristic where the one carburetor barrel serves a multitude of chambers to the point where the individual carburetor barrels are serving their respective chambers, there may be a lag or uneven mixture distribution when the additional carburetor barrels come into operation.
It is, therefore, a principal object of this invention to provide an improved induction system for a multiple cylinder multiple carburetor barrel internal combustion engine.
It is another object of the invention to provide an improved throttle control system for a multiple cylinder multiple carburetor barrel internal combustion engine.
It is a further object of the invention to provide an improved throttle control and induction system for a multiple carburetor barrel multiple cylinder engine wherein one of the carburetor barrels supplies a plurality of cylinders only during certain engine operating characteristics.